1. Field of the Invention
The present invention relates to a magnetic recording device for providing security related information. The present invention also relates to processes for the preparation of such a device and a process for the application of the device in association with an object to be identified.
The storage of information on a magnetic recording carrier in a coded format and the identification of an object bearing the magnetic carrier, through reading the information on the carrier, are known. It is conventional to use magnetic carriers containing coded information for the identification of such objects as credit cards, payment tickets, financial papers, cards for gaining access to certain geographic locations and cards for gaining access to a place during a certain period of time, for example.
A magnetic recording carrier of this type can consist of a film of a resinous material comprising individual grains of magnetic particles, for example acicular, i.e., needlelike, particles of gamma Fe.sub.2 O.sub.3 or any other magnetized particle. Such carriers are generally prepared from a suspension of the component grains in a solution with a solvent of resinous binder. The solution is coated on a magnetically inert carrier in the form of a film by conventional means. Following evaporation of the solvent, a film of the magnetic product of magnetizable grains and resin, having a substantially constant thickness, remains on the carrier. The magnetizable grains can have either a random orientation or a predetermined orientation which is established prior to the evaporation of the solvent.
A magnetic carrier formed in this manner can then be placed on the object to be identified or personalized and coded magnetic information is recorded on the carrier by means of known devices. For example, the recording can be carried out by means of directional pulses. Thereafter, by reading this recorded information in a magnetic decoding device, it is possible to compare the information stored in the carrier with a reference signal and determine whether the object bearing the information conforms with an object which is anticipated. Due to the relative ease with which the coded information can be read from the carrier, this system for identifying objects is susceptible to forgeries. The forgeries can be accomplished merely be reproducing the coded information on a virgin magnetic recording carrier, such as one manufactured in the manner described previously, after reading the information from the bearer object.
2. Description of the Prior Art
One proposed solution for eliminating forgeries consists of preorienting the acicular grains in predetermined zones by means of pulses which are applied after the coating of the suspension during the manufacture of the magnetizable carrier. This orientation of the grains results in the creation of zones in the magnetizable carrier which exhibit physically undetectable differences in remanence, i.e., residual magnetism. A signal which is recorded on such a carrier produces a response in a magnetic reader which cannot be reproduced on an ordinary carrier. After reading the signal recorded on the carrier, the signal is erased by the reader mechanism, and is therefore not susceptible of being copied on an ordinary carrier, in view of the difference in remanence between the genuine carrier and a forged carrier.
The inhibition of forgery through this technique has a disadvantage in that it requires skilled operations to preorient the magnetizable grains in a desired pattern, and therefore increases the cost of the manufacture of the information carrier.